This invention relates to a process for catalytically hydrogenating alkyne-containing feeds which also comprise sulfur impurities.
The selective hydrogenation of alkynes, which generally are present in small amounts in alkene-containing streams (e.g., acetylene contained in ethylene streams from thermal ethane crackers), is commercially carried out in the presence of alumina-supported palladium catalysts. In the case of the selective hydrogenation of acetylene to ethylene, preferably an alumina-supported palladium/silver catalyst is used in accordance with the disclosure in U.S. Pat. No. 4,404,124 and its division, U.S. Pat. No. 4,484,015. The operating temperature for this hydrogenation process is selected such that essentially all acetylene is hydrogenated to ethylene (and thus removed from the feed stream) while only an insignificant amount of ethylene is hydrogenated to ethane (to minimize ethylene losses and to avoid a "runaway" reaction which is difficult to control, as has been pointed out in the above-identified patents).
It is generally known by those skilled in the art that sulfur impurities (such as H.sub.2 S, COS, mercaptans and organic sulfides) when present in alkyne-containing feeds can poison and deactivate these palladium-containing catalysts. The present invention is directed to the use of an improved palladium catalyst in the selective hydrogenation alkynes to alkene, in particular of acetylene to ethylene, in the presence of sulfur-containing impurities.